The invention relates to food tray-containing carts of the general type used by airlines and hospitals to hold food until it is ready to be served. More particularly, the invention relates to the mechanism by which the food trays are kept in a chilled condition from the time they leave the place of preparation until they are removed from the cart. As noted in copending Dodd application Ser. No. 321,852, filed Nov. 16, 1981, the majority of known cart systems for holding trays use one cart or a portion thereof for holding trays in a chilled atmosphere and another cart or a portion thereof for holding the containers for the hot portion of the meal. The hot meal containers are commonly fully cooked and then merely kept warm in the cart, or else they are partially cooked and kept warm and then brought up to a high temperature before serving. An example of a system wherein a portion of a cart is chilled while another portion is heated is disclosed in Vernon U.S. Pat. No. 3,517,899. Examples of improved systems wherein the hot and cold foods are positioned on a single tray which is kept in a refrigerated atmosphere, with the hot containers being heated by underlying heater plates before serving, are disclosed in Shulz et al., U.S. Pat. No. Re. 30,623 and in Dodd et al., U.S. Pat. No. 4,346,756. Each of the aforementioned applications and reissue patent are assigned to the same assignee as the present application and their disclosures are incorporated by reference herein.
The aforementioned Dodd application, Ser. No. 321,852 discloses a chilling system which utilizes a tray or bunker member containing dry ice or other cooling material to eliminate much of the weight, expense and space requirements of mechanical refrigeration systems which are built into aircraft. The particular bunker member disclosed has an opening in its end wall at its inlet end which is adapted to abut a blower fan mounted in the cart. This particular arrangement, although quite functional, permits the bunker to be installed from only one end of the cart, whereas airlines would probably prefer to be able to install it from either end since they are accustomed to loading food trays from either end. The position of the blower in horizontal alignment with the removable bunker causes it to be exposed to possible damage from the careless use of high pressure steam or hot water hoses used to clean the carts after every use. Finally, since the flat interior bottom of the disclosed bunker would prevent air from contacting the entire bottom surface of the dry ice pieces, it was found desirable to position a second layer of dry ice on top of a perforated plastic intermediate shelf member to maximize the cooling rate.